The present invention relates to an adjusting drive with a closed housing, with an outwardly extending actuating member movable to and fro between two end positions by means of an electric motor and with a force transmission arranged in the same housing which during the operation of the electric motor transmits forces from its driving member connected with the shaft of the electric motor to its output member connected with the adjusting member.
An electrical adjusting drive of the aforementioned type is known from the DE-OS No. 28 45 844. This actuating or drive mechanism provided for use in central locking systems of motor vehicles includes in its housing an electric motor reversible in its direction of rotation and for the force transmission, a speed-reduction planetary gear transmission and an electromagnetically actuated friction clutch whose magnet winding is electrically connected in parallel with the electric motor. As a result thereof, only with a turned-on electric motor the torque existing at the transmission output is transmitted by way of the friction linings of the clutch to the adjusting member movable to and fro between two end positions which protrudes out of the housing. The relative movability achieved therewith between the adjusting member and a turned-off motor permits an easy manual actuation of the latching parts of the lock connected with the adjusting member by way of a linkage or jointed drive without the need that a slack or bridgeable detent device has to be provided in this linkage, as is the case in other known central locking systems.
However, by reason of the electromagnetic clutch, the energy requirement of the drive arrangement is very high. The friction linings of the clutch are parts subject to wear, and it may happen that by reason of residual magnetism the coil spring acting opposite the magnetic force is not able to separate the friction linings after the current is turned off. Furthermore, with each adjusting operation larger masses (planetary gear, friction disks) have to be accelerated in a rotary sense within a short period of time and have to be brought to standstill again in an equally short period of time. A high dynamic stressing of all force-transmitting members between the electric motor and the adjusting member results therefrom which becomes effective in a wear-enhancing manner if the running time of the adjusting drive is not to be designed relatively long in a comfort-reducing manner.
The present invention is concerned with the task to so construct an electric adjusting drive of the aforementioned type that the force transmission between the electric motor and the adjusting member does not require any energy input of its own, cannot block and permits short adjustment durations for each adjusting operation without high dynamic stresses and loads.
The underlying problems are solved according to the present invention in that the driving part of the force transmission is constructed as pump with reversible feed direction, in that the output part of the force transmission is constructed as working element movable by fluidic pressure forces produced by the pump, and in that the pump and working element are arranged inside of the housing within a fluidic system, out of which the adjusting member is extended in a pressure-tight member.
The use of a fluidic force transmission between the electric motor and the adjusting member reduces the weight of the movable parts of the adjusting drive and therewith, on the one hand, the power input thereof and, on the other, the dynamic load of the force transmission. Additionally, such an arrangement also operates nearly wear-free and noiselessly. Both hydraulic as also pneumatic components can be used in the system of the present invention even though the pneumatic force transmission is preferred. The latter can be operated with a simple pump and a light diaphragm piston working element in a weight-saving and reliable manner and therebeyond raises no special problems with sealing the closed fluidic system, especially does not raise any such problems when the system air is under atmospheric pressure in the rest or inoperative condition. It may be necessary to provide in the pneumatic system slight defined leakages to the surrounding atmosphere, for example, sinter throttles or the like, within a housing wall in order that under all circumstances the pressure difference necessary for the displacement of the working element can be built up at the working element and a rate of fluid flow, even though small, is always assured at the pump.
By the simultaneous actuation of the piston working element on one piston side with excess pressure and on the other piston side with vacuum, respectively, vice versa, depending on the adjusting direction of the adjusting member, respectively, feed direction of the pump, the effective areas of the piston and the space content of the fluidic system can be kept small with relatively high adjusting forces.
As a result thereof, the following advantages are achieved:
compact adjusting drive housing, PA1 slight cushioning effect of the compressed air, PA1 very short running periods of motor and pump per adjusting operation by reason of the small volumetric rate of flow in the pump. PA1 simple, reliable feed and control connections; PA1 rapid start during engagement and PA1 high reliability, PA1 low-wear and low-noise operation; PA1 small dynamic loads by reason of smaller movable masses; PA1 simple construction; PA1 ease of operation in the rest or inoperative condition; and PA1 fluidic system combining the function of speed reduction PA1 transmission and clutch.
The two last-mentioned advantages are also important in a comparison of the adjusting drive according to the present invention with known components of electro-pneumatic central locking systems. In such systems, for example, as described in the DE-PS No. 31 49 071, a central motor-pump-unit is provided which actuates the single-chamber lock-adjusting elements connected to a pump pressure nipple by way of hose lines alternately with excess pressure, respectively, vacuum for unlocking and locking the locks coordinated thereto. Another pressure nipple of the pump is open toward the atmosphere; the fluidic system is therefore alternately vented and exhausted.
As a result thereof, the volumetric rate of flow of the pump and therewith the length of life thereof and the cushion effect of the air transported in the system become large. Additionally, for purposes of multi-position actuation of the central motor-pump-unit, electrical lines to the key-operated locks must be provided in addition to the hose connections.
Above all during the preassembly of motor vehicle doors with their entire equipments inclusive central locking elements, plug-type connections must be provided for each hose line which are then plugged together during the assembly of the completed door at the body with the corresponding pump connection lines. In comparison to electric plug-type connections, the pneumatic plug elements mechanically stressed by pressure forces are exposed to considerably larger loads and stresses and therebeyond form also undesirable throttling places in the course of the hose lines.
A working element coordinated to the motor-pump-unit is already mentioned in the system according to the DE-PS No. 31 49 071 and is correspondingly illustrated in the figure. However, differing from the adjusting drive according to the present invention, this working element is connected only with an electric switch--for the limit de-energization of the electric motor--and is connected only on one side with the pump, in parallel with the further pneumatic lock adjusting elements. Additionally, it responds later than the lock-adjusting elements, i.e., requires a longer running period of the pump.
A pneumatic brake force servo device is disclosed in the DE-OS No. 22 32 956 whose piston, for purposes of force increase, is acted upon by a pump simultaneously on one side with excess pressure and, on the other side, with vacuum. As in the adjusting drive according to the present invention, the pressure difference between the two piston sides is therefore increased in this publication. Consequently, smaller dimensions of the working element can be realized. At the same time, however, an excess pressure and a vacuum storage device each are provided in the fluidic system of this prior art brake force servo-device so that this publication provides no indication for a compact adjusting drive with simultaneous excess pressure and vacuum actuation of a working element in a closed fluidic system having a small fluid volume.
The adjusting drive according to the present invention combines the advantages of the electric motor, i.e.,
with those of a fluidic, especially pneumatic force transmission, i.e.,